Gas discharge device



May 14, 1957 MALTER ET AL GAS DISCHARGE DEVICE Filed Nov. 21. 1952 INVE NTORS j Lou/s MALTA-7?,

[aw/m0 0. Jam/Sofia?- WILL/4M M WEESTEE, Je

United tates GAS DISCHARGE DEVICE Application November 21, 1952, Serial No. 321,892 12 Claims. (Cl. 315-168) This invention relates to electron discharge devices and circuits therefore of the type in which an ionizable medium is employed to support a discharge. More particularly, this invention relates to electron discharge devices and the related circuits wherein large currents may be drawn to an electrode with small applied potentials.

This invention specifically relates to gas discharge devices and circuits of the type wherein the function of ionizing the gaseous medium is separated from the load current path through the device. Prior to this invention the separation of the ionizing discharge from the load current path has required the provision of a plurality of thermionic cathodes. At least one of these cathodes has been necessary to provide electrons to ionize the gaseous medium while another cathode has been necessary to provide electrons for the load current. This requirement of at least two thermionic cathodes in tubes of this type has increased the cost of this type of discharge devices as well as the cost of the associated circuits.

It is an object of this invention to provide a new and improved gas discharge device wherein large currents may be drawn to an electrode that has small applied potentials.

It is another object of this invention to provide a new and improved gas discharge device requiring only one thermionic cathode and wherein the ionizing potential is separated from the load current path.

It is a further object of this invention to provide a new and novel gas discharge device utilizing a high degree of ionization per unit of auxiliary discharge current.

A still further object of this invention is to provide a new and novel circuit utilizing a gas discharge device constructed in accordance with this invention. 7

These and other objects are attained in accordance with the general aspects of this invention by providing a gas discharge device comprising a single thermionic cathode that provides electrons for an auxiliary discharge and also provides electrons for the main load current. This is accomplished by means of utilizing a constricting type of electrode to increase the degree of ionization for a given auxiliary discharge, and in one embodiment by utilizing the constricting electrode as an anode.

The novel features which are believed to be characteristic of this invention are set forth with particularity in the appended claims. The invention itself will best be understood by referring to the follownig description taken in connection with the accompanying drawings in which:

Figure 1 is a tranverse sectional view of a gas discharge device constructed in accordance with this invention through the line 11 of Figure 2;

Figure 2 is a sectional view thereof through line 2-2 of Figure 1;

Figure 3 is a schematic diagram showing a novel method of operating the gas discharge device shown in Figures 1 and 2;

' atent Figure 4 is a schematic diagram showing a method of operating the gas discharge device shown in Figures 1 a stem 12 through which lead=in conductors are sealed in the usual manner. The electrode assembly is supported by means of the conductors within the envelope as indicated. Between upper and lower insulating members 13 and 14 are mounted a thermionic cathode 15, an apertured electrode 16, and an auxiliary anode 18. Cathode 15 is the usual oxide coated sleeve type cathode having a noninductive type heater extending therein, leads 19 of which are connected to support conductors 20 and 21. The cathode 15 is electrically energized through a lead-in conductor 22. The upper end of cathode 15 is crimped in the well known manner to lock the same in place between the insulating members 13 and 14.

The apertured electrode 16 surrounds the thermionic cathode 15, as shown, and has an aperture 17 therein. The apertured electrode 16 is supported betwen insulating members 13 and 14 by support rods 23 and is electrically energized through support rod 24 which is in turn con nected to a lead-in. The aperture 17 is an elongated slot opening in the direction of the auxiliary anode 18.

Auxiliary anode 18 is a conventional metallic plate supported between insulating members 13 and 14 by support rods in the well known manner and is energized by means of a support rod 25 as is shown.

Having described the basic characteristics of this type of gas discharge device, further description of the construction of this device is not deemed necessary. However, if further description is required, it may be found by referring to an article appearing in IRE, volume 40, No. 6, June 1952, page 645, by the present inventors.

Gas discharge device 10 is processed in the usual manner. It is exhausted and gettered and then filled with a suitable ionizable medium. Any of the well known gaseous or vaporizable material known in the gas discharge art may be utilized, though one of the rare gases is preferred and in particular helium or argon. The gas pressure may vary from approximately microns to several millimeters of mercury. The device now being described for the purpose of illustrating the invention was filled with helium at a pressure of 750 microns.

Referring now to Figure 3 to best understand the operation of the device, there is shown a schematic diagram of the gas discharge device described in connection with Figures 1 and 2; Connected between the thermionic cathode 15 and the apertured electrode 16 is a load 27 and a source 28. Also connected to cathode 15 is a resister 3%), a source of potential 31 and an input terminal 33. The other side of the input terminal is connected to the auxiliary anode 18. In order for the device to function properly, an auxiliary discharge is maintained by the thermionic cathode 15 and auxiliary anode 18. In order" to maintain the auxiliary discharge, the potential difference between thermionic cathode 15 and auxiliary anode 18 must be greater than the ionization potential of the gaseous filling. When the auxiliary discharge occurs, the electrons from thermionic cathode 15 produces a plasma in the region between apertured electrode 16 and auxiliary anode 18. The positive ions that are formed in the plasma'drift back into the area enclosed by'the apertured electrode 16 so that a plasma is present inthis region.

1; Patented May 14,1957

When the plasma is present in the area surrounded by the apertured electrode 16, a relatively small potential, i. e. approximately 1 or 2 volts, applied to apertured electrode 16 by means of source 28, permits extremely large currents to be drawn to the load 27. Currents of over a 100 milliamperes have been drawn to the' apertured electrode 16 although the voltage dilference between apertured electrode 16 and thermionic. cathode 15 was less than two volts. I

The gas discharge device shown in Figure '3 may be modulated by applying a signal to the terminals 33 as shown which will vary the auxiliary discharge current which, varies the plasma density and, consequently, the load current. V

In Figure 4 there is shown an embodiment of the circuit diagram shown in Figure 3 that is specifically designed for rectifier type of operation. In this embodiment of the circuitry for the gas discharge device 10, the thermionic cathode 15 is connected to auxiliary anode 18 through a source 34 and a resistor 35. The magnitude of the potential dilference between these electrodes is greater than the ionization potential of the gaseous filling and thus fills the device with a plasma. Connected between thermionic cathode and apertured electrode 16 is a load 36 and input terminals 37. When an input signal is applied across terminals 37, the device will conduct during the portion of the cycle when apertured electrode 16 is positive with respect to thermionic cathode15. It should be understood that conventional filter circuits may be used as part of load 36. This modifica tion of the circuitry utilizes simple on oif control.

Referring now to Figure 5, there is shown a transverse sectional view of an embodiment of this invention comprising a thermionic cathode 40 partially surrounded by a U-shaped control electrode 41 and a U-shaped main anode 42. At the open end of the U-shaped control electrode-anode structure is a constricting electrode 43 having an opening 44 opening toward an auxiliary anode 45. The electrodes are supported on insulating member 46 and are held in position by support rods 47 in a conventional manner as shown.

In this embodiment of the invention, the constricting electrode 43 may be left floating, connected to cathode 40, or for some purposes, may be connected to the control electrode 41. The electrodes are supported in a conventional manner similar to the supports described in connection with Figures 1 and 2 so that further description of the electrode supporting structure is not deemed necessary.

In operation of this embodiment of the invention, a potential difierence that is greater than the ionization potential of the medium is applied between thermionic cathode 40 and auxiliary anode 45. This difference in potential causes an ionizing discharge to occur between these two electrodes, i. e. from cathode 40 to anode 45. The ionizing discharge is constricted by constricting electrode 43 so that the discharge occurs close to aperture 44 in the apertured electrode-auxiliary anode region and thus causes a dense plasma to be formed. These ions, because of the voltage gradient between cathode 40 and main anode 42, difiuse back through the aperture 44 into the region of the main load current path and thus locates a plasma in this region.

A potential ditference less than the ionization potential of the medium is applied between thermionic cathode 40 and main anode 42. The presence of the plasma in the region between cathode 40 and anode 42 permits large currents to be drawn to main anode 42 with small applied potentials. When it is desired to modulate the electron flow to main anode 42, a modulating potential is applied to control electrode 41. This modulating po tential will have continuous control of the electron flow to main anode 42. A more thorough description of the continuous control of a control electrode in this type 4 V of gas discharge device may be found in the above identified co-pending application.

Referring now to Figure 6, there is shown a still further embodiment of this invention comprising a therrnionic cathode 50 partially surrounded by a U-shaped control electrode 51 and a U-shaped main anode 52. At the open end of the U-shaped control electrode-anode structure is a constricting electrode 53 having an apertured narrow channel extension 53 extending toward thermionic cathode 50. Adjacent opening 54 in the apertured electrode 53 is an auxiliary anode 55. The V electrodes are supported in a conventional manner on insulating member 56 by means of support rods 57.

In operation of this embodiment of the invention, a potential difference greater than the ionization potential of the ionizable medium is applied between thermionic cathode 50 and auxiliary anode 55. This potential difference causes an ionizing discharge to occur between these electrodes. The ionizing discharge forms a large number of positive ions in the space between thermionic cathode 50 and auxiliary anode 55, i. e. in the narrow channel extension 53'. A great portion of these positive ions diffuse through the apertures of the narrow channel portion 53 of-the constricting electrode 53 into the main current path and thus produce a very dense plasma in this region. The apertured electrode 53 is preferably connected to thermionic cathode 50 or may be left floating as is desired. a g

A difference of potential less than the ionization potential of the medium is applied between thermionic cathode 50 and main anode 52. This difference in potential causes a current of considerable magnitude to be drawn to main anode 52 with a small applied potentials. The control electrode 51 modulates the electron flow to main anode 52 as was described in connection with Figure 4. Due to the apertures in the channel portion 53' of the constricting electrode 53, a high degree of ionization per unit of auxiliary discharge current will be present in the region between thermionic cathode 50 and main anode 52.

It is believed obvious that though we have shown several specific embodiments and have described our invention in connection therewith, an invention is subject to wide variations and modifications without departing from the spirit thereof. It is, therefore, intended to cover all such modifications which come within the scope ofthe appended claims.

We claim:

1. A gas discharge device, comprising a sealed envelope having an ionizable medium therein, an electrode assembly within said envelope including a thermionic cathode and two independent anodes within said envelope, said cathode and one of said anodes defining an ionizing discharge path for ionizing said medium and forming a plasma extending substantially between said cathode and both of said anodes, and said electrode assembly having means including the other of said anodes for constricting said ionizing discharge path, said cathode and said other of said anodes defining a load current path.

2. A gas discharge device, comprising a sealed envelope having an ionizable-medium therein, a single thermionic cathode and two independent anodes within said envelope, said cathode and one of said anodes defining an auxiliary discharge path for ionizing said medium and forming a plasma in said envelope, said plasma normally extending from adjacent said cathode to adjacent both of said anodes, and means including the other of said anodes for constricting said auxiliary discharge path,'said cathode and said other of said anodes defining a load current path in said envelope.

3. A gas discharge device, as in claim 2 further comprising a control electrode intermediate said cathode and said other of said anodes. v

4. A gas discharge device, comprising a sealed envelope having an ionizable medium therein, a single thermionic cathode within said envelope, an apertured anode spaced around said cathode, a second anode spaced from said apertured anode, said cathode and said second anode defining an ionizing discharge path for ionizing said medium and forming a plasma in said envelope, said plasma normally extending from adjacent both of said anodes, the aperture of said apertured anode being arranged whereby it constricts said ionizing discharge, and said cathode and said apertured anode defining a load current path in said envelope.

5. A gas discharge device, comprising a sealed envelope having an ionizable medium therein, a thermionic cathode within said envelope, a U-shaped main anode spaced around said cathode, a control electrode intermediate said cathode and said U-shaped anode, an auxiliary anode spaced from the open end of said U-shaped anode, said cathode and said auxiliary anode defining an ionizing discharge path for ionizing said medium and forming a plasma in said envelope, a constricting electrode intermediate said open end of said U-shaped anode and said auxiliary anode and having a slot therein for constricting said ionizing discharge, and said cathode and said U-shaped anode defining a load current path in said envelope.

6. A gas discharge device as in claim 5 further comprising an elongated apertured channel extending from said constricting electrode substantially to said cathode.

7. A gas discharge device, comprising a sealed envelope having an ionizable medium therein, a single thermionic cathode within said envelope, a U- spaced around said cathode, an auxiliary anode spaced from the open end of said main anode, said cathode and said auxiliary anode defining an ionizing discharge path for ionizing said medium and forming a plasma in said envelope, an apertured constricting electrode intermediate said auxiliary anode and said cathode for constricting said ionizing discharge path, an elongated apertured channel extending from the aperture in said apertured electrode to said cathode whereby the particles of said plasma difluse therethrough, and said cathode and said main anode defining a main load current path through said device.

8. Gas discharge apparatus, comprising a gas discharge device having a gas tight envelope with an ionizable medium therein having a predetermined ionization potential, an array of load circuit electrodes defining a load current path and including a thermionic cathode and a main anode partially surrounding said cathode, an array of ionizing electrodes for producing a plasma substantially throughout said load current and including said thermionic cathode and an auxiliary anode; a load impedance having one side connected to said cathode, a' source of potential less than said ionization potential connected between the other side of said load impedance and said main anode, an ionizing circuit including a source of potential greater than said ionization potential connected between said cathode and said auxiliary anode.

haped main anode 9. Gas discharge apparatus as in claim 8 wherein said ionizing circuit further comprises a signal source for modulating the density of the plasma formed by said array of ionizing electrodes.

10. Gas discharge apparatus, comprising a gas discharge device having a gas tight envelope with an ionizable medium therein having a predetermined ionization potential, an array of load circuit electrodes defining a load current path and including a thermionic cathode and a main anode partially surrounding said cathode, an array of ionizing electrodes for producing a plasma substantially throughout said load current path and including said thermionic cathode and an auxiliary anode; a load impedance having one side connected to said cathode, a source of potential less than said ionization potential connected between the other side of said load impedance and said main anode, a source of potential greater than said ionization potential having one side connected to said cathode, and the other side of said last named source being connected to said auxiliary anode through a current limiting resistance and a signal source.

11. Gas discharge apparatus, comprising a gas discharge device having a gas tight envelope with an ionizable medium therein having a predetermined ionization potential, an array of load circuit electrodes including a thermionic cathode and a main anode at least partially surrounding said cathode, an array of ionizing electrodes for ionizing the medium substantially throughout said load current path and including said cathode and an auxiliary anode; a load impedance having one side connected to said cathode, a signal source connected between the other side of said load impedance and said main anode, a source of potential greater than said ionization potential having one side connected to said cathode, the other side of said last named source being connected to said auxiliary anode through a current limiting resistance.

12. A gas discharge device comprising, a sealed envelope having an ionizable medium therein, a thermionic cathode, a first anode spaced from said cathode, said cathode and said first anode forming an ionizing discharge path for ionizing said medium and forming a plasma in said envelope, at second anode partially surrounding and spaced from said cathode whereby said ionizing discharge is constricted, said cathode and said second anode defining a load current path through said device.

References Cited in the file of this patent UNITED STATES PATENTS 1,917,739 Schroter July 11, 1933 2,158,564 Meier May 16, 1939 2,226,171 Lecorquillier Dec. 24, 1940 2,450,475 Hansell Oct. 5, 1948 2,565,103 Toulon Aug. 13, 1951 2,607,021 Von Gugelberg Aug. 12, 1952 2,612,617 Hagen Sept. 30, 1952 

